Seismic Collapse Risk Assessment of Braced Frames under Near-Fault Earthquakes

Zhenqiang Wang,Gaofeng Jia,Jeet Kumar Sonwani,Hussam N. Mahmoud

doi:10.3390/met11081271

Abstract

Special concentrically braced frames (SCBFs) located in regions close to earthquake faults may be subjected to near-fault ground motions, often characterized by pulses with long periods. These near-fault pulses could impose additional seismic demands on structures and increase the risk for structural collapse. Currently, there is limited research on the seismic collapse risk of SCBFs under near-fault earthquakes. This paper uses a general simulation-based framework to assess the seismic collapse risk of SCBFs under near-fault earthquakes. To quantify the large variability and uncertainty associated with the seismic hazard, a stochastic ground motion (SGM) model is used where the near-fault pulse characteristics are explicitly incorporated. The uncertainties in the SGM model parameters (including the near-fault pulse characteristics) are addressed through appropriate selection of probability distribution functions. To accurately predict the occurrence of collapse, numerical models capable of capturing the nonlinear and collapse behavior are established and used. Efficient stochastic simulation approaches are proposed to estimate the seismic collapse risk with or without considering the near-fault pulse. As an illustration, the seismic collapse risks of two SCBFs are investigated and compared. Probabilistic sensitivity analysis is also carried out to investigate the importance of uncertain model parameters within the SGM towards the seismic collapse risk.

Highlights

One of the most crucial objectives of the building codes is life safety, which is ensured by protecting structures against collapse under seismic events
To investigate the seismic collapse risk of special concentrically braced frames (SCBFs) under near-fault earthquakes, this study used a general simulation-based framework, which facilitates the adoption of complex models and the consideration of various sources of uncertainties associated with the structure and the seismic hazards
This paper investigated the significance of the near-fault pulse on the seismic collapse risk of SCBFs close to earthquake faults

Summary

Introduction

One of the most crucial objectives of the building codes is life safety, which is ensured by protecting structures against collapse under seismic events. How the seismic hazard characteristics and near-fault pulse characteristics impact the seismic collapse risk is still not well understood These challenges hinder better understanding of seismic collapse performance and the risk of structures close to earthquake faults. To investigate the seismic collapse risk of SCBFs under near-fault earthquakes, this study used a general simulation-based framework, which facilitates the adoption of complex models and the consideration of various sources of uncertainties associated with the structure and the seismic hazards. Probabilistic sensitivity analysis was carried out to investigate the importance of each (or groups of) uncertain model parameters within the SGM including the near-fault pulse characteristics towards the seismic collapse risk of the two example braced frames. Quantification of Seismic Collapse Risk of Braced Frames under Near-Fault Earthquakes

Simulation-Based Framework for Seismic Collapse Risk Quantification

Stochastic Near-Fault Ground Motion Model

Stochastic Simulation for Seismic Collapse Risk Assessment

Efficient Estimation of Conditional Seismic Collapse Risk

Probabilistic Sensitivity Analysis Using Sample-Based Approach

Illustrative Example

The Example Braced Frames

Numerical Modeling of the Example Braced Frames

Chevron-Braced Frame

Cross-Braced Frame

Comparison between the Two Braced Frames

Probabilistic Sensitivity Analysis Results